The research described here has shown that bainitic rail steel can be produced to hardness well over 400 HB by air cooling the appropriate chemistry without the requirement of additional and sometimes complex cooling techniques. The fracture toughness of the bainitic steel tested is above that commonly seen in head-hardened pearlitic steel rails. This increased toughness increases the critical crack size before sudden fracture, potentially increasing the probability of finding cracks by ultrasonic inspection before rail failure. Laboratory tests and full-scale tests with axle loads up to 35.7 tonnes have shown that the rolling contact fatigue performance of bainitic steel rail appears to be superior to that of head hardened pearlitic rails. Especially in full-scale service tests, the bainitic rail steel showed much better resistance to rolling contact fatigue cracks and spalls than did head-hardened pearlitic steel. The causes of this apparent superiority in RCF performance are not understood. Laboratory and full-scale tests with axle loads up to 35.7 tonnes have led to conflicting wear results. In some tests, the bainitic steel has performed better than head-hardened pearlitic rail steel; in other tests, performance has been worse. The causes of these conflicting results are also not known. But a higher natural wear rate can still lead to increased rail life if there is less need for grinding to remove RCF defects. Finally, the research has indicated that more knowledge is needed about wear/RCF/metallurgy interactions, and about thee measurement and influence of shear yield strength. Work at UIUC, sponsored by the AAR and the FRA is focused on developing this knowledge.
Wear and rolling contact fatigue in bainitic steel microstructures
2003
10 Seiten, 12 Bilder, 8 Tabellen, 13 Quellen
Conference paper
English
Wear and rolling contact fatigue in bainitic steel microstructures
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